1. Field of the Invention
The present invention relates to a cooling apparatus for an electronic device having a thin machine body such as a mobile computer, a digital video camera and the like.
2. Description of the Prior Art
Conventionally, the thin electronic device of this kind is structured such that a mounting board 3 mounting a heat-generating circuit part 2 such as a semiconductor, a CPU and the like is arranged within a casing 1 as shown in FIG. 5, and a heat generated by the circuit part 2 is discharged out of the device via a heat transmission member 4 made of an aluminum plate or the like.
Here, in a heat discharge amount to an outer portion due to a heat transmission, the following relation (1) is established.
Qoutxe2x88x9dxcexa3(Tsixe2x88x92Ta)xc3x97Sixe2x80x83xe2x80x83(1)
Qout: heat discharge amount
Tsi: temperature of a fine portion at i number when separating a surface of the casing into fine portions
Si: area of the fine portion at i number mentioned above
Ta: temperature of the open air
Accordingly, the temperature of the casing increases as a calorific power of the heat generating part to be cooled increases, and an area of a portion having a high temperature becomes widened in accordance therewith.
In accordance with the structure mentioned above, since the electronic device such as a mobile computer or a digital video camera is used by being held by a hand, an increase of the temperature of the surface of the casing gives an uncomfortable feeling to a user and may cause problems with of the device in some cases.
In this view, there has been developed an electronic device in which a fan is provided within the electronic device so as to forcibly discharge the heat generated within the casing to an outer portion.
FIG. 6 shows an embodiment of the electronic device provided with a cooling fan. The electronic device is structured such as to arrange a plurality of mounting boards 3 mounting heat-generating circuit parts 2 such as semiconductors and the like within the casing 1. The electronic device is further structured such as to shorten a length of the mounting board 3 in a side of an inner bottom within the casing 1 so as to form a space with respect to a side surface of the casing 1, to arrange a flat type cooling fan 5 having a frame serving as a heat sink in the space so that a minimum size thereof corresponds to a direction of thickness of the device, to transmit a heat generated in the circuit parts 2 to the cooling fan 5 via a heat transmission member 4 made of an aluminum or the like, and to forcibly discharge the heat out of the device body by an operation of the cooling fan 5.
In a thin note type personal computer, the structure mentioned above is frequently employed, and it is desired to design a thin type electronic device so as to secure a sufficient reliability, to restrict a height of the cooling fan 5 to about 7.5 mm and to set a thickness of the device within 20 mm.
However, the electronic device shown in FIG. 6 has the following problems.
That is, in the case of the electronic device such as the mobile type personal computer having a significantly thin thickness, it is desired to further reduce the height of the cooling fan and reduce the occupied space in a direction of the thickness, so that it is hard that the device using the normal motor, for example, an outer rotor type motor satisfies the desire.
Further, when the mounting portion is constituted by two sheets of mounting boards having a size of 50 mmxc3x97100 mm, the parts mounting area is expressed by the following formula.
50 mmxc3x97100 mmxc3x972 (surfaces)xc3x972 (sheets)=20000 mm2
When one of the mounting boards 3 is notched for arranging the cooling fan 5, a non-mounting area is expressed by the following formula since the size of the cooling fan 5 is 40 mmxc3x9740 mm.
xe2x80x8340 mmxc3x9740 mmxc3x972 (surfaces)=3200 mm2
Accordingly, the parts mounting area is reduced by 16%.
This causes a great limitation for designing an electronic device having a compact size, a high performance and a high function.
An object of the present invention is to provide a cooling apparatus for an electronic device provided with a cooling fan having a compact size, a high performance and a high function, which can structure the cooling fan so as to reduce an occupied space in a direction of a thickness, to be easily assembled and reduce a parts mounting area as less as possible, thereby securing a thinness of the electronic device.
In order to achieve the object of the present invention, in accordance with the present invention, there is provided a cooling apparatus for an electronic device comprising a mounting board mounting electronic parts including heat generating parts such as semiconductors and arranged within a casing of a thin type electronic device such as a mobile personal computer and a digital video camera, and a cooling fan installed therein, wherein a flat cooling fan is constituted by a motor comprising a flat stator and a flat rotor opposing to a surface of the flat stator, a vane provided in the flat rotor of the motor and a frame, the cooling fan is arranged within the casing so that a height direction thereof corresponds to a direction of a thickness of the casing, and the heat generating parts on the mounting board and a frame of the cooling fan are thermally connected by a heat transmission member.
As mentioned above, since the structure is made such that the height of the cooling fan can be reduced to a significantly low level, the cooling fan can be easily assembled within the thin type casing and arranged on a partial surface of the mounting board, so that the electronic device with the cooling fan having a compact size, a high performance and a high function can be achieved without greatly reducing the area of mounting the parts on the mounting board and the heat generated by the heat generating parts within the electronic device can be sufficiently radiated so as to cool the heat generating parts. Accordingly, in the electronic device provided with the cooling apparatus such as the mobile type personal computer, the digital video camera and the like, the thin structure can be realized without reducing the cooling effect and without reducing the area for mounting the parts.